Not sure if this is a bug or just because I don't know what I'm doing, but I get a problem on line 37294 of ext-all-debug.js. this.componentLayout.lastComponentSize is undefined. It is happening with some grids I am dynamically creating and adding to a panel. if the grid is on the first panel, it works fine, but for the panels that are not showing yet, I get this bug, and layout of any further components stops.

I have modified my copy of ext-all-debug.js to check for the condition, and now my app works as expected